1. Field of the Invention
The invention relates generally to the field of communications. More particularly, the invention relates to a polar modulator.
2. Discussion of the Related Art
The cellular communication industry has been striving to create networks that allow consumers to use their services anywhere. Designing RF front ends for multimode telephones and base stations has been a difficult task, however, polar modulation technology has been developed to facilitate the design of such systems.
A polar modulator can independently process a carrier's amplitude and phase signals, typically working together with a nonlinear power amplifier operating in switched mode. The elimination of the linear operation requirement enables the power amplifier efficiency to be maximized for each modulation standard.
Under a polar modulation scheme, multimode operation may be achieved by digital switching. Phase information is used to tune a voltage-controlled oscillator (VCO) driving the power amplifier, while amplitude information modulates the power amplifier according to the standard required.
Unfortunately, polar modulator transmitters do not always meet signal quality specifications determined by current industry standards. What is needed is a method and apparatus for improving signal quality in a polar modulation system.